/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.reactive.result.method.annotation;

import java.util.Collections;
import java.util.List;
import java.util.function.Function;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import reactor.core.publisher.Mono;

import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.ReactiveAdapterRegistry;
import org.springframework.http.codec.HttpMessageReader;
import org.springframework.http.codec.ServerCodecConfigurer;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.web.bind.support.WebBindingInitializer;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.reactive.BindingContext;
import org.springframework.web.reactive.HandlerAdapter;
import org.springframework.web.reactive.HandlerResult;
import org.springframework.web.reactive.result.method.InvocableHandlerMethod;
import org.springframework.web.server.ServerWebExchange;

/**
 * Supports the invocation of
 * {@link org.springframework.web.bind.annotation.RequestMapping @RequestMapping}
 * handler methods.
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
public class RequestMappingHandlerAdapter implements HandlerAdapter, ApplicationContextAware, InitializingBean {

    private static final Log logger = LogFactory.getLog(RequestMappingHandlerAdapter.class);


    private List<HttpMessageReader<?>> messageReaders = Collections.emptyList();

    @Nullable
    private WebBindingInitializer webBindingInitializer;

    @Nullable
    private ArgumentResolverConfigurer argumentResolverConfigurer;

    @Nullable
    private ReactiveAdapterRegistry reactiveAdapterRegistry;

    @Nullable
    private ConfigurableApplicationContext applicationContext;

    @Nullable
    private ControllerMethodResolver methodResolver;

    @Nullable
    private ModelInitializer modelInitializer;

    /**
     * Return the configurer for HTTP message readers.
     */
    public List<HttpMessageReader<?>> getMessageReaders() {
        return this.messageReaders;
    }

    /**
     * Configure HTTP message readers to de-serialize the request body with.
     * <p>By default this is set to {@link ServerCodecConfigurer}'s readers with defaults.
     */
    public void setMessageReaders(List<HttpMessageReader<?>> messageReaders) {
        Assert.notNull(messageReaders, "'messageReaders' must not be null");
        this.messageReaders = messageReaders;
    }

    /**
     * Return the configured WebBindingInitializer, or {@code null} if none.
     */
    @Nullable
    public WebBindingInitializer getWebBindingInitializer() {
        return this.webBindingInitializer;
    }

    /**
     * Provide a WebBindingInitializer with "global" initialization to apply
     * to every DataBinder instance.
     */
    public void setWebBindingInitializer(@Nullable WebBindingInitializer webBindingInitializer) {
        this.webBindingInitializer = webBindingInitializer;
    }

    /**
     * Return the configured resolvers for controller method arguments.
     */
    @Nullable
    public ArgumentResolverConfigurer getArgumentResolverConfigurer() {
        return this.argumentResolverConfigurer;
    }

    /**
     * Configure resolvers for controller method arguments.
     */
    public void setArgumentResolverConfigurer(@Nullable ArgumentResolverConfigurer configurer) {
        this.argumentResolverConfigurer = configurer;
    }

    /**
     * Return the configured registry for adapting reactive types.
     */
    @Nullable
    public ReactiveAdapterRegistry getReactiveAdapterRegistry() {
        return this.reactiveAdapterRegistry;
    }

    /**
     * Configure the registry for adapting various reactive types.
     * <p>By default this is an instance of {@link ReactiveAdapterRegistry} with
     * default settings.
     */
    public void setReactiveAdapterRegistry(@Nullable ReactiveAdapterRegistry registry) {
        this.reactiveAdapterRegistry = registry;
    }

    /**
     * A {@link ConfigurableApplicationContext} is expected for resolving
     * expressions in method argument default values as well as for
     * detecting {@code @ControllerAdvice} beans.
     */
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) {
        if (applicationContext instanceof ConfigurableApplicationContext) {
            this.applicationContext = (ConfigurableApplicationContext) applicationContext;
        }
    }


    @Override
    public void afterPropertiesSet() throws Exception {
        Assert.notNull(this.applicationContext, "ApplicationContext is required");

        if (CollectionUtils.isEmpty(this.messageReaders)) {
            ServerCodecConfigurer codecConfigurer = ServerCodecConfigurer.create();
            this.messageReaders = codecConfigurer.getReaders();
        }
        if (this.argumentResolverConfigurer == null) {
            this.argumentResolverConfigurer = new ArgumentResolverConfigurer();
        }
        if (this.reactiveAdapterRegistry == null) {
            this.reactiveAdapterRegistry = ReactiveAdapterRegistry.getSharedInstance();
        }

        this.methodResolver = new ControllerMethodResolver(this.argumentResolverConfigurer,
                this.messageReaders, this.reactiveAdapterRegistry, this.applicationContext);

        this.modelInitializer = new ModelInitializer(this.methodResolver, this.reactiveAdapterRegistry);
    }


    @Override
    public boolean supports(Object handler) {
        return HandlerMethod.class.equals(handler.getClass());
    }

    @Override
    public Mono<HandlerResult> handle(ServerWebExchange exchange, Object handler) {
        HandlerMethod handlerMethod = (HandlerMethod) handler;
        Assert.state(this.methodResolver != null && this.modelInitializer != null, "Not initialized");

        InitBinderBindingContext bindingContext = new InitBinderBindingContext(
                getWebBindingInitializer(), this.methodResolver.getInitBinderMethods(handlerMethod));

        InvocableHandlerMethod invocableMethod = this.methodResolver.getRequestMappingMethod(handlerMethod);

        Function<Throwable, Mono<HandlerResult>> exceptionHandler =
                ex -> handleException(ex, handlerMethod, bindingContext, exchange);

        return this.modelInitializer
                .initModel(handlerMethod, bindingContext, exchange)
                .then(Mono.defer(() -> invocableMethod.invoke(exchange, bindingContext)))
                .doOnNext(result -> result.setExceptionHandler(exceptionHandler))
                .doOnNext(result -> bindingContext.saveModel())
                .onErrorResume(exceptionHandler);
    }

    private Mono<HandlerResult> handleException(Throwable exception, HandlerMethod handlerMethod,
            BindingContext bindingContext, ServerWebExchange exchange) {

        Assert.state(this.methodResolver != null, "Not initialized");

        InvocableHandlerMethod invocable = this.methodResolver.getExceptionHandlerMethod(exception, handlerMethod);
        if (invocable != null) {
            try {
                if (logger.isDebugEnabled()) {
                    logger.debug("Invoking @ExceptionHandler method: " + invocable.getMethod());
                }
                bindingContext.getModel().asMap().clear();
                Throwable cause = exception.getCause();
                if (cause != null) {
                    return invocable.invoke(exchange, bindingContext, exception, cause, handlerMethod);
                } else {
                    return invocable.invoke(exchange, bindingContext, exception, handlerMethod);
                }
            } catch (Throwable invocationEx) {
                if (logger.isWarnEnabled()) {
                    logger.warn("Failed to invoke: " + invocable.getMethod(), invocationEx);
                }
            }
        }
        return Mono.error(exception);
    }

}
